1. Field of the Invention
This invention relates generally to the field of blow molded plastic containers, and specifically to a hot fill type container having a dome portion that is shaped to provide superior crush resistance.
2. Description of the Related Technology
Many products that were previously packaged using glass containers are now being supplied in plastic containers, such as containers that are fabricated from polyesters such as polyethylene terephthalate (PET).
PET containers are typically manufactured using the stretch blow molding process. This involves the use of a preform that is injection molded into a shape that facilitates distribution of the plastic material within the preform into the desired final shape of the container. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it takes on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold.
Hot fill containers are designed to be used with the conventional hot fill process in which a liquid or semi-solid product such as fruit juice, sauce, salsa, jelly or fruit salad is introduced into the container while warm or hot, as appropriate, for sanitary packaging of the product. After filling, such containers undergo significant volumetric shrinkage as a result of the cooling of the product within the sealed container. Hot fill type containers accordingly must be designed to have the capability of accommodating such shrinkage. Typically this has been done by incorporating one or more vacuum panels into the side wall of the container that are designed to flex inwardly as the volume of the product within the container decreases as a result of cooling. However, some hot fill type containers are designed without vacuum panels, and are engineered to assume vacuum uptake through inward deflection of features of the container, such as the dome portion.
The dome portion of a blow molded plastic container forms the shoulder of the container and is typically positioned between an upper finish portion that defines an opening and is designed to receive a closure. The dome portion of certain types of predecessor hot fill containers was prone to denting as a result of physical contact and vacuum forces within the container. While it is possible to strengthen the dome portion by engineering it to have a thicker sidewall, this is problematic in the sense that it requires more material to make the container, which adds to the expense of the container.
A need therefore exists for a hot fill container having a dome configuration that provides superior crush resistance with respect to predecessor containers without significantly increasing material costs.